In the prior art there has been developed a wide variety of systems for producing useful work. Some of the systems, such as nuclear fission, suffered from bad publicity. Others such as conversion of energy content of substances such as wood, coal and petroleum, are suffering from scarcity of the fuel and from pollution by the waste products of combustion. Consequently, there is increasing emphasis on the use of solar energy and similar readily available fuels that do not contaminate. The systems for using solar energy are referred to as solar systems. These systems have taken a wide variety of forms ranging from using the collectors alone to amplifying type collectors. The collectors have ranged from collections of photovoltaic cells that convert the radiant energy directly into electrical energy to more mundane systems that convert the energy to heat for heating a fluid for use; for example, in generation of power.
Regardless of which system is employed, it is generally conceded to be beneficial to employ a principle in which the sun's radiant energy from a much larger area than a single collector, per se, is made use of.
In a typical installation heretofore, the collector was mounted on an expensive tower or the like that held the collector high for directing the energy onto it; and many reflectors, generally referred to as heliostats, were spaced about the central collector and used sensors for directing the radiant energy onto the collector.
In a patent by co-workers Floyd Blake and Lynn Northrup, Jr. and assigned to the assignee of this invention, entitled "Solar System Having Improved Heliostat and Sensor Mountings", U.S. Pat. No. 4,227,513, the descriptive matter of which is incorporated herein by reference for details that are omitted herefrom, there was disclosed an improvement that eliminated the prior major expense of having to have the reflectors mounted on one post and the sensors mounted on another post, both of the posts being deeply embedded in the earth's surface such that they were firmly anchored and resisted receiving minor surface movements that were independent of each other. In that patent application there was disclosed an improved co-mounted reflector and sensor on a single post to eliminate that nonfunctional and inefficient expense.
Despite that improvement, it has been found functionally, flexibly, and economically advantageous to eliminate the sensor, per se; and to control the heliostats by a computer that calculates respective commanded positions to which the heliostats are moved in respective azimuths and elevations for a given time of the day.
On the other hand, banks of photovoltaic cells can be arranged to resemble the heliostats and thereafter controlled by a similar computer control to maximize received solar energy.
Typical of the art employing a controller to attain a position for aiming a collector or heliostat so as to maximize the received energy from the sum are the following U.S. Pat. Nos. 4,107,521 describes an improved solar sensor and tracker apparatus in which low cost high-angular accuracy sensor and tracking device use symmetrical sensor shade and sensor arrangement to track the sun. No. 4,146,785 describes a solid state control system for control of a collector array in which there is incorporated sun tracking mode, defocusing at excessive temperatures, returning to standby after sunset and pre-positioning at sunrise. That patent contains a fairly good description of typical prior art approaches employing these sensors and describes its invention in automating these respective elements. No. 4,223,174 describes solar energy converter assemblies having sensors for following the sun. No. 4,223,214 also describes the solar tracking arrangement using sensors. No. 4,215,410 describes a computer controller for positioning a solar collector to point towards the sun and receive the maximum amount of energy responsive to a correlation between the physical, geographical location and the time of day. No. 4,267,441 shows energy ray tracking device for fixing the direction to receive maximum energy rays. No. 4,215,410 contains an excellent description of the prior art approach for orienting a collector to receive the maximum rays. No. 4,243,018 describes a solar energy concentrator mounted to extend longitudinally in an east-west direction spaced above a supporting surface for pivotal movement to receive solar energy in a focused manner. All of these systems provided relatively complicated approaches.
In a co-pending application by one of the inventors, James A. Kaehler, entitled "Improved Heliostat Control", Ser. No. 342,155 with a filing date of Jan. 25, 1982, U.S. Pat. No. 4,440,150, and assigned to the assignee of this invention, there was disclosed an improved system employing stepping motors in which the computer calculated the number of steps of the respective stepping motors.
In all of the foregoing, there was required expensive sub-assembly such as the stepping motors or the like. It is desirable that the controls be simple, automatic, easily implemented and not require expensive sub-assemblies; yet, provide a flexible way of controlling one or more collectors to maximize solar energy reception or controlling the heliostats to reflect the solar energy onto a collector, when multiple heliostats were employed in an array of many heliostats about a collector.